I've had another half-playthrough since this thread started, and this time I really tried to pay close attention to Shadowheart's responses and behavior to see if I had missed anything. Ultimately, though, I still didn't see enough to think that she wasn't going to carry out her quest.
It seems like it could be fixed with some updated dialogue options, though: "Remain silent. You sense Shadowheart's reluctance." or something like that.
One aspect that I am still taken aback by is
how quickly she goes from trusting you to declaring that she's going to murder you on the spot. And it never comes up again.
No follow up. No apology. No recognition that she just threatened to murder her ally and confidant for having the audacity to - gasp! - gently suggest that she think this whole thing over.
